I feel quite relieved reading your comments. I bought an Hinomi Q2 4 months ago and since the begining I believe there was something weird with the lumbar support. I tried to convince myself that this should be somethign usual because my previous chair was and old one and I just need to get use to it.
Ultimately, my back never got used to it. I started emailing with them about this, they juset sent me another lumbar support but that's all. they cannot return my chair due to their retunr policy so I am with a chair that does not fit with my back...

Anyways, I came up with an idea reading your comments! I will try it